In the widely used Internet, service is requested and provided in a one-to-one relationship between a sender and a receiver using an IP address. However, various fields and applications using the Internet such as Internet high-definition TV, Internet voice/picture communication, Internet remote control, Internet of Things (IoT) have been continuously developed and used. Accordingly, service request and provision in this one-to-one relationship have limitations in terms of scalability, security, and service quality due to limitations in the number of IP addresses.
In order to overcome these limitations, researches on the future Internet are underway. The researches are largely divided into an evolutionary approach and a revolutionary approach. In the evolutionary approach, the current basic characteristics of the Internet are maintained and service continuity is ensured. On the other hand, the revolutionary approach creates new network technologies that are not bound or bound to current Internet technologies, and that can fully meet the needs of future societies.
Among the above revolutionary approaches, a content centric network system (CCN) requests and provides a service based on a content name instead of requesting and providing a service in a 1:1 relationship using the conventional IP address.
FIG. 1 is a diagram for illustrating a conventional content centric network system. FIG. 2 and FIG. 3 are diagrams for illustrating a process of transmitting and receiving contents in a conventional content centric network system.
Referring to FIG. 1, the conventional content centric network system includes a network 20 including a plurality of local routers, and a user device 10 and a content server 30 connected to the network 20.
The user device 10 is connected to one of the plurality of local routers included in the network 20 and transmits the content request message to the connected local router. The connected local router extracts an identifier for the requested content from the content request message and determines whether the requested content is stored and registered in the connected local router based on the requested content identifier. If the requested content does not exist in the connected local router, the connected local router transmits the content request message in a flooded manner to neighboring local routers included in the network 20. Next, a neighboring local router storing and registering the requested content therein among the neighboring local routers, or a source local router connected to the content server 30 providing the requested content, transmits the requested content to the user device 10 in the reverse order of the routing flow of the content request message.
Referring to FIG. 2, the user device 10 transmits the content request message CR including information on the requested content to the connected local router A. The connected local router A compares the requested content identifier with the content identifier list stored and registered in the connected local router A, thereby determining whether the requested content exists in the connected local router A. If the requested content does not exist in the connected local router A, the connected local router A transmits the content request message to a neighboring local router B thereto. The neighboring local router B determines whether the requested content exists in the neighboring local router B or not. If the requested content does not exist in the neighboring local router B, the neighboring local router B transmits the content request message to another adjacent neighboring router C thereto. If the requested content is not registered and stored in the neighboring local router C, the neighboring local router C transmits the content request message to another local router D adjacent thereto. The neighboring local router D may be a source local router connected to the content server 30 providing the requested content. In response to the content request message CR, the source local router D transmits a content response message CP including the requested content along a reverse path of the receive path of the content request message CR. That is, the content response message CP is transmitted to the local router C adjacent to the source local router D, then to the neighbor local router B, and then to the connected local router A. each of the local routers B, C, and D located in the transmission path of the content response message CP may register and store the requested content included in the content response message in its own storage unit.
As shown in FIG. 3, when there is a request for the same content from another user device 40, the requested content is not provided to the user device 40 from the server 30 storing the requested content. Instead, the requested content is provided directly to the user device 40 from the neighboring local router C that has stored the requested content. By doing so, the requested content can be provided quickly.
However, in the conventional content-based network system described above, the same content is stored in all the local routers in the routing path between the server providing the content and the user device or between the local router storing the content and the user device. Therefore, the substantially identical contents are redundantly stored in the local routers of the routing paths. As a result, various types of contents cannot be distributed among and stored in the local routers, each router having a limited amount of cache.
Further, since the substantially identical contents are redundantly stored in the local routers of the routing paths, various contents requested from the user device are less likely to be provided directly to the user device. Also, since the local router cannot directly provide the content to the user device, but the content stored in the server is provided to the user device, the traffic load increases.
Since the connected local router transmits the content request message in a flooded manner to the neighboring local routers in the network, it takes a lot of network load to transmit the content request message.